1. Field of the Invention
The present invention relates to an airbag apparatus in which a pad-side mounting leg portion of a pad cover is affixed to a base-side mounting leg portion of a base member.
2. Description of the Related Art
Generally, an airbag apparatus for a driver seat comprises: a bag holder which is supported by a steering wheel; an inflator which is affixed to the bag holder and which ejects gas when a vehicle decelerates rapidly; a bag which is kept in a folded state in the vicinity of the inflator; and a pad cover which houses the bag and the inflator between the bag holder and itself, and breaks open and unfolds when a bag inflation pressure which exceeds a predetermined value is exerted.
Conventionally, the pad cover is affixed to the bag holder as described below. That is, as illustrated in FIG. 6, a plate lock 102 is provided to the surface of the bag holder 100 at the side opposite to the vehicle occupant side. The leg portion for mounting 110 which is configured so as to protrude to the back surface of the pad cover 108 is nipped between the support leg portion 104 of the bag holder 100 and the nipping portion 106 of the plate lock 102. The bag holder 100, the plate lock 102 and the pad cover 108 are fixed in this state by fixing means such as bolts, nuts and the like. Incidentally, the plate lock 102 is mainly used in the four-spoke type steering wheel, and a bracket is used in the three-spoke type steering wheel. Adopting the above-described structure ensures that when the pad cover unfolds, the unfold load is supported by the bag holder 100 and the pad cover 108 is thereby prevented from flying off.
However, in the case of the above structure, the leg portion for mounting 110 of the pad cover 108 is held by two members, namely, the support leg portion 104 of the bag holder 100 and the nipping portion 106 of the plate lock 102. As a result there is the disadvantage that the number of parts are increased and thereby cost is increased.
A structure in which the effect of the above-described structure is attained with one member is disclosed in Japanese Laid-Open No. 11-48895, and is briefly described below.
In the airbag apparatus disclosed in this publication, a plurality of cover mounting portions which are equivalent to the nipping portion of the above-described plate lock, are formed integrally with a side wall portion of the base plate which is equivalent to the above-described bag holder. The mounting wall portion is provided at the covering body, which is equivalent to the pad cover. By the mounting wall portion of the covering body being inserted between the side wall portion of the base plate and the cover mounting portion, the side wall portion of the base plate and the cover mounting portion are claw-fit together with the mounting wall portion of the covering body.
However, in the case of the airbag apparatus disclosed in the above-mentioned publication, because the two wall portions (i.e., the side wall portion and the cover mounting portion) which are disposed so as to be in close proximity to and parallel with each other must be formed integrally with a base plate formed of metal, accurate manufacturing work of the air bag entails difficulty.
In light of the above, an object of the present invention is to provide an airbag apparatus in which a pad cover can be securely supported on a base member and the manufacturing work is facilitated.
In the first aspect of the present invention, an airbag apparatus comprises: a high rigidity base member including a base portion to which an inflator which ejects gas when a vehicle rapidly decelerates and a bag which is inflated by the gas are fixed, and a base-side mounting leg portion which is provided at the base portion; and a pad cover formed of resin including a top portion which houses the bag between the base portion of the base member and the top portion, and is provided with an unfolding portion which breaks open and unfolds when an inflation pressure exerted by the bag exceeds a predetermined value, and a pad-side mounting leg portion which is affixed to the base-side mounting leg portion provided on a surface which is opposite to a vehicle occupant side of the top portion; wherein said airbag apparatus further comprises: an engagement mechanism which engages the pad-side mounting leg portion and the base-side mounting leg portions with each other; an obstruction mechanism which includes: spaces which are formed between the pad-side mounting leg portion and support walls provided at the pad-side mounting leg portion and; insertion portions, which are inserted into the spaces provided on the base-side mounting leg portion; such that a releasing of an engagement state of the pad-side mounting leg portion and the base-side mounting leg portion, due to elastic deformation in an unfolding direction of the unfolding portion of the pad cover, is prevented.
The second aspect of the present invention is the airbag apparatus of the first aspect wherein, the engagement mechanism is formed of engagement protrusions which are formed on one of the base-side mounting leg portion and the pad-side mounting leg portion, and engagement openings which are formed on the other of the base-side mounting leg portion and the pad-side mounting leg portion, such that the engagement protrusions can engage with engagement openings.
The third aspect of the present invention is the airbag apparatus of the first aspect wherein, the base end portions of the support walls are integrally formed with the surface which is opposite to the vehicle occupant side of the pad cover.
The fourth aspect of the present invention is the airbag apparatus of the first aspect wherein, the obstruction mechanism obstructs the movement of the insertion portion in directions orthogonal to the engagement and removal directions of the pad-side mounting leg portion and the base-side mounting leg portion.
The fifth aspect of the present invention is the airbag apparatus of the second aspect, further comprising a guide member which guides the engagement of the pad cover and the base member.
The sixth aspect of the present invention is the airbag apparatus of the fifth aspect wherein, the guide member is a taper portion which is provided at a distal end portion of the pad-side mounting leg portion, and guides the engagement of the engagement protrusion formed at the base-side mounting leg portion with the engagement holes formed at the pad-side mounting leg portion.
The seventh aspect of the present invention is the airbag apparatus of fifth aspect wherein, the guide member is a triangular engagement protrusion, when viewed from the side, which is formed on the pad-side mounting leg portion, and guides the engagement of the engagement protrusion with the engagement hole which is formed on the base-side mounting leg portion.
The eighth aspect of the present invention is the airbag apparatus of fifth aspect wherein, both end portions, in a pad cover circumferential direction, of at least one of the support walls are affixed to pad-side mounting leg portion.
According to a first aspect, when the airbag is in a state in which it is not actuated, the pad-side leg for mounting and the base-side leg for mounting are in a state in which they are engaged with each other by the engagement mechanism. Accordingly, in this state, there is no possibility that the pad cover will come apart from the base member.
When there is a rapid deceleration of the vehicle, gas is ejected from the inflator and the bag which is in a folded state is inflated by this gas. At this time, when the bag inflation pressure exceeds a predetermined value, the unfolding portions which are provided at the top portion of the pad cover break open and are unfolded. At this time, the pad-side mounting leg portion also receives force in the unfolding direction from the unfolding portion, and because it attempts to elastically deform in the unfolding direction, there is a possibility that the state in which the pad-side mounting leg portion and the base-side mounting leg portion are engaged by the engaging means, may be released.
However, in the present invention, the insertion portions of the base-side mounting leg portion are inserted into spaces formed between the pad-side mounting leg portion and support walls formed thereto. Thus when the pad-side mounting leg portion attempts to elastically deform in the direction in which the unfolding portion unfolds, the support walls and the insertion portions interfere with each other. As a result, the state in which base-side mounting leg portion and the pad-side mounting leg portion are engaged is prevented from being released.
In view of the above, in the present invention, secure mounting of the pad cover to the base member is ensured, and when there is a rapid deceleration of the vehicle, the pad cover which unfolds is securely supported by the base member.
Further, in the present invention, the pad-side mounting leg portion and the support walls provided thereto, achieve the role of the two wall portions in the prior art. That is to say, in the present invention, by providing two wall portions to the pad cover which is formed of a resin, the manufacturing work is considerably facilitated when compared with the case in which, the two wall portions are provided to a very hard (for example metal) base member.
According to the second aspect, an engagement mechanism is formed of: engagement protrusions formed on one of the base-side mounting leg portion or the pad-side mounting leg portion; and engagement openings formed on the other one (of the base-side mounting leg portion and the pad-side mounting leg portion) and to which the engagement protrusions can be engaged. As a result of this structure, in a case where the engagement protrusions are formed on the base-side mounting leg portion, because the base member is very hard, when the engagement protrusions engage with the engagement openings, they are in a state in which they are firmly fixed. On the other hand, in a case where the engagement protrusions are formed on the pad-side mounting leg portion, only the engagement openings are formed on the base-side mounting leg portion. Even in a case in which the base member is formed of metal, in order to form the engagement openings it is sufficient to just carry out the hole punching operation, and the operation of bending in order to form the engagement protrusion becomes unnecessary.
According to the third aspect, because the base end portion of the support walls which are provided on the pad-side mounting leg portion is integrally formed with the back surface of the top portion of the pad cover, the strength of the support walls is increased.